[CM] Add timestamp to backup file

[ycombinator]

Consider the following scenario:

1. User enrolls a filebeat instance. The user's filebeat.yml gets backed up as filebeat.yml.bak.
2. User un-enrolls the instance.
3. User makes changes to their filebeat.yml.
4. User re-enrolls the instance. The user's filebeat.yml gets backed up as filebeat.yml.bak, overwriting their previous filebeat.yml.bak.

If the user wants to peruse the contents of their original filebeat.yml, they cannot do that any more.

Perhaps we should add a timestamp portion somewhere in the .bak filename?

[ph]

I will add this, I think that will help since we are still in the beta state.